Proposed resolution:

This wording is relative to N5014.

1. Modify [alg.merge], as indicated:

   template<class InputIterator1, class InputIterator2,
            class OutputIterator>
     constexpr OutputIterator
       merge(InputIterator1 first1, InputIterator1 last1,
             InputIterator2 first2, InputIterator2 last2,
             OutputIterator result);
   […]
   template<execution-policy Ep, sized-random-access-range R1, sized-random-access-range R2,
            sized-random-access-range OutR, class Comp = ranges::less,
            class Proj1 = identity, class Proj2 = identity>
     requires mergeable<iterator_t<R1>, iterator_t<R2>, iterator_t<OutR>, Comp, Proj1, Proj2>
     ranges::merge_result<borrowed_iterator_t<R1>, borrowed_iterator_t<R2>, borrowed_iterator_t<OutR>>
       ranges::merge(Ep&& exec, R1&& r1, R2&& r2, OutR&& result_r,
                     Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
   

   -1- Let:

   • (1.1) — N be: […]
   • (1.2) — `comp` be `less{}`, `proj1` be `identity{}`, and `proj2` be `identity{}`, for the overloads with no parameters by those names;
   • (1.3) — E(e1, e1) be bool(invoke(comp, invoke(proj2, e2), invoke(proj1, e1)));
   • (1.4) — K be the smallest integer in `[0, last1 - first1)` such that for the element `e1` in the position first1 + K there are at least N − K elements `e2` in `[first2, last2)` for which E(e1, e1) holds, and be equal to `last1 - first1` if no such integer exists.

   -2- Preconditions: The ranges `[first1, last1)` and `[first2, last2)` are sorted with respect to `comp` and `proj1` or `proj2`, respectively. The resulting range does not overlap with either of the original ranges.

   -3- Effects: Copies the first K elements of the range `[first1, last1)` and the first N − K elements of the range `[first2, last2)` into the range [result, result + N). If an element `a` precedes `b` in an input range, `a` is copied into the output range before `b`. If `e1` is an element of `[first1, last1)` and `e2` of `[first2, last2)`, `e2` is copied into the output range before `e1` if and only if E(e1, e1) is `true`.

[ Kona 2025-11-08; Status changed: Immediate → WP. ]

[ Kona 2025-11-07; approved by LWG. Status changed: New → Immediate. ]

The original text of the “US 163-262” issue says: “Bullets 1.3 and 1.4 and paragraph 3 should say E(e1, e2) instead of E(e1, e1)” in [alg.merge]. The problem, though, was introduced when merging P3179R9 “Parallel Range Algorithms” proposal. The original wording of P3179 does not have parentheses after E. Those extra parameters in E do not bring clarity to `merge` algorithm. The proposed resolution is to strike them through.